In the production of microelectronic devices, integrated circuitry may be formed in and on semiconductor wafers. Semiconductor wafers may be composed primarily of silicon, although other materials such as gallium arsenide and indium phosphide may be used. As shown in FIG. 1, a single microelectronic device wafer 10 may contain a plurality of integrated circuits (ICs) 12, that may be substantially rectangular and arranged in rows and columns. Two sets of mutually parallel scribe streets 14 may extend perpendicular to each other over substantially the entire surface of the semiconductor wafer 10 between each discrete integrated circuit 12. Scribe streets may also be referred to as scribe lines.
After the integrated circuits 12 have been subjected to preliminary testing for functionality (wafer sort), the microelectronic device wafer 10 may be diced (or cut apart) so that each area of functioning integrated circuitry 12 becomes a microelectronic die that can be used to form a packaged microelectronic device. One example microelectronic wafer dicing process uses a circular diamond-impregnated dicing saw that travels down two mutually perpendicular sets of scribe streets 14 lying between each of the rows and columns. The scribe streets 14 are sized to allow passage of a wafer saw blade between adjacent integrated circuits 12 without causing damage to the circuitry.
As shown in FIGS. 2 and 3, the microelectronic device wafer 10 may also include guard rings 16 that substantially surround the integrated circuits 12. As shown in FIG. 3, the guard rings 16 may extend through a plurality of metallization layers 18. The metallization layers 18 may include layers of metal traces separated by layers of dielectric material layers on a semiconductor wafer 20. The metallization layers 18 provide routes for electrical communication between integrated circuit components within the integrated circuits 12. The guard ring 16 may be formed layer by layer as each of the metallization layers 18 is formed. The guard ring 16 may assist in preventing external contamination encroaching into the integrated circuitry 12 between the metallization layers 18.
Prior to dicing, the microelectronic device wafer 10 may be mounted onto a sticky, flexible tape 22 (shown in FIG. 3) that is attached to a ridge frame (not shown). The tape 22 may continue to hold the microelectronic die after the dicing operation and during transport to the next assembly operation. As shown in FIGS. 4 and 5, the saw may cut a channel 24 in the scribe street 14 through the metallization layers 18 and the semiconductor wafer 20. During cutting, the saw may cut into the tape 22 up to about one-third of its thickness, for example.
However, in the dicing of microelectronic device wafers 10, the use of industry standard dicing saws (metal impregnated with diamond) may result in a rough edge along the metallization layers 12. This may be more prevalent with a metallization layer having ductile copper traces. This rough edge is a source of crack propagation into and/or delamination of the metallization layers 18, through the guard ring 16, and into the integrated circuitry 12 causing fatal defects. These defects may increase as the device material properties move toward weaker adhesions and strengths in order to meet various electrical property requirements.
Therefore, it would be advantageous to develop techniques to effectively dice microelectronic device wafers while reducing or substantially eliminating the possibility of crack and delamination propagation.